Compressor for refrigeration



July 18, 1961 A. c. sAMPlETRo 2,992,636

COMPRESSOR RoR RRRRIGERATION Filed Nov. 5, 1956 3 Sheets-Sheet 1 July 18, 1961 A, Q sAMPlETRQ 2,992,636

COMPRESSOR FOR REFRIGERTION Filed Nov. 5, 1956 N 3 Sheets-Sheet 2 m, @M @wf WM 222mg July 18, 1961 A. c. sAMPlETRo 2,992,636

COMPRESSOR FOR REFRIGERATION Filed NOV. 5, 1956 5 Sheets-Sheet 3 Q MM? ML/MHH@ United States Patent 2,992,636 COMPRESSOR FOR REFRIGERAI'ION Achilles C. Sampietro, Detroit, Mich., assignor to Thompson Ramo Wooldridge luc., a corporation of Ohio Filed Nov. 5, 1956, Ser. No. 620,280 3 Claims. (Cl. 121-164) The present invention relates to improvements in free piston gas compressors operated by pressurized operating fluid and relating to improved control valves for the operating uid and improved means for positioning the control valves.

The invention more specifically contemplates the ernployment of a free compression piston slidably housed in a compression cylinder provided with valve controlled intake and delivery ports for receiving a fluid or gas such as is used in a refrigeration system `and for delivering the gas in a compressed state such as to the expansion nozzle of a refrigeration system.

The free compression piston may be operated by operating pistons secured to project from the ends of the compression piston and be slidably housed in operating cylinders extending beyond the compression cylinder. The compression piston will be of larger diameter than the operating piston for the utilization of an operating fluid of higher pressure than the `gas or Huid to be compressed. The operating pistons are alternately forced toward the compression piston to cause a reciprocation thereof and the pressurized operating fluid supplied by a compressor is alternately supplied to one of the operating pistons while being returned from the operating cylinder of the opposite operating piston. The supply and return of pressurized operating iiuid is controlled by operating fluid control valves having valve chambers projecting coaxial from the ends of the operating cylinders and having valve spools movable within the chambers between a fluid supply position and a liuid return position. The valve spools project into the cylinders in their uid return position to be physically engaged by the operating piston in its return stroke whereby the valve is pushed to the fluid supply position. Simultaneously, the movable valve spool for the opposing operating piston is moved to the return position by a pressure responsive valve positioner which is supplied operating fluid when the srt valve is pushed by the operating piston.

*In another form the valves Iare coaxially positioned and the valve spools are operated by a rotary cam positioned between them.

An object of the invention is to provide an improved free piston fluid operated gas compressor for `a refrigeration system or the like.

Another object of the invention is to provide a free piston compression mechanism compressing gas in a double stroke action and operated with an improved pressurized fluid operating mechanism.

Another object of the invention is to provide an improved compressor wherein an operating fluid is used, which is at a higher pressure than the uid or gas to be compressed.

Another object of the invention is to provide a driving mechanism for a reciprocating gas compressor wherein the driving mechanism is operated by a compressed uid and employs an improved :duid supply and control system, which achieves rapid and automatic control of iiuid and smooth rapid and efiicient reciprocation of the compressor.

A still further object of the invention is to provide an improved valving system for controlling the supply of trolled by a valve which projects into the path of the operating piston to be engaged and positioned thereby in its path of travel.

A further object of the invention is to provide an improved spool valve for regulating the flow of fluid to a reciprocating fluid operating piston whereby the spool valve is instantaneously and automatically positioned by direct engagement with the piston and by the pressure of the operating iuid.

Other objects and advantages will become more apparent with the complete teaching of the invention in the disclosure of the preferred embodiments thereof in the specification and claims taken in connection with the appended drawings, in which:

FIGURE 1 is a partially diagrammatic view of the system for supplying gas and for supplying operating fluid to the compressor with the compressor and iluid control system being illustrated and certain mechanisms of the system being shown in sectional view;

FIGURE 2 is a sectional view of a form of the compressor and operating mechanism and the valve structure used to control the supply of pressurized operating fluid to the operating mechanism; and,

FIGURE 3 is also a sectional view of the compressor and operating mechanism with another form of the control valve arrangement that is used.

FIGURE l illustrates the mechanism for supplying gas or the like to be compressed at 6 and illustrates the mechanism for supplying the pressurized operating Huid generally at 8. The compressor and control unit is shown generally Lat 10 within the confines of the broken line enclosure and alternate forms of compressors and control units which may be used in place of that illustrated in FIGURE l, are shown in FIGURES 2 and 3.

It will be understood that the drawings and description teaching the principles of the invention employ the preferred embodiments thereof, but other embodiments and variations may be employed, `as will be recognized by those skilled in the art, utilizing the advantages, teachings and features of the invention. Also, the features of the invention may be utilized in other environments without adhering to the system shown herein in which the invention enjoys particular advantages.

The gas or material to be compressed may be of various types depending upon the circumstances in which the mechanism is to be employed` As illustrated, however, the compressor may be used in the refrigeration system wherein the gaseous refrigerant is supplied from a container 12 to a precompressor 14, which is illustrated as being a turbine. The turbine is driven by an electric motor 16, supplied electricity through leads 18 and 20 from an electrical supply such as a battery 22. The battery is maintained in its charged state by `a generator 24, which is provided with the usual voltage regulating circuitry 26. As is illustrated the system may be utilized in an automobile, wherein the electrical supply is obtained from the generator and battery arrangement, and fthe compressor used in the refrigeration system of an air conditioner.

The pressurized operating fluid is furnished by the compression mechanism 8, which includes a uid compressor 28, which has an intake line 30 connected to a uid supply tank 32. The compression pump 28 pumps the iiuid through a line 34 connected to a pressure relief valve 36. In normal operation the iiuid leaves the pressure relief valve 36 to enter a supply line 38.

The pressure relief valve 36 operates in a known manner having a spring loaded plunger 40 with an upper face exposed to the pressure of vthe iiuid in the supply line. When this pressure reaches 'an excessive amount, the coil compression spring 42 supporting the plunger 40, is compressed to where Ithe lateral passageways 44 are brought 3 into alignment with the pressure relief line 46, and the pressurized fluid escapes through the line 46 into the valve housing and down through the return line 48 into the `reservoir tank 32. This by-passes the fluid from the supply line 3S until the pressure has dropped suliiciently for the valve plunger 40 to return to its operating position, Yas shown in FIGURE 1.

The gas supply from the compressor 14, is delivered to the compressor and control unit through the gas supply conduit 50. The gas supply branches to s-upply gas to the two intake conduits 52 and 54 leading into opposite ends of a compression cylinder 56.

The compression cylinder 56 contains a compression piston 58, slidably mounted therein so as to be capable of being driven in a reciprocating motion to compress the gas taken into the cylinder 56. The gas is` delivered through gas delivery conduits 60 and 62, which lead from opposite ends of the compressing piston 5S. The gas intake conduits 52 and 54, which lead in through ports into the compressing cylinder, are provided with non-retum valves 64 and 66, respectively. The gas delivery conduits 60 and 62 are likewise provided with non-return valves 68 and 70, which permit the gas to be forced out of the compressor cylinder S6, but prevent its return. The gas is delivered -to a conduit 72 from the two conduits 60 and 62, and conduit 72 leads to the location Where the compressed gas is to be delivered, shown by way of illustration as an expansion nozzle 74 for a refrigeration system.

In order to reciprocate the compressor piston 58, opposed operating pistons 76 and 78 are connected to the compressor piston 58 and are forced back and forth Within their operating cylinders S0 and 82. These cylinders are shown as being formed integral with the compression cylinder 56. The compression cylinder or chamber 56 is larger `in cross-sectional area than the chambers of the operating cylinders 30 and 82 since the operating lluid will be under higher pressure than the compressed gas.

The operating pistons 76 and 78 are forced back and forth to move the free compressor piston 58 by alternate admission and return of operating fluid to each of the operating cylinders. Pressurized lluid is admitted to the operating cylinder v80, shown at the left in FIGURE 1, through the pressure line 84. The pressurized operating liuid is supplied and returned from the cylinder 82, at the right of the compression mechanism, as shown in FIGURE l, through the conduit 86.

When the left operating cylinder 80 is being supplied with pressurized fluid, the right cylinder 82 is relieved so that the fluid can return to a return line. The return line is shown 'at 88 and leads back to the reservoir 32.

Operating fluid control valves 90 and 92 are connected between the fluid supply line 38 andthe conduits 84 and 86 leading to the opposed operating cylinders. The left valve, as shown in FIGURE l, includes a valve housing 94 having a spool valve 96 slidable therein. The right valve yalso includes a valve housing 98 with a spool valve 100 slidably mounted therein. The valve spools project beyond their valve housing or body Iand are in engagement with a rotating cam 102. As the cam rotates, it `alternately positions the valve spools so that one of the operating cylinders will be connected to the pressurized fluid supply line 38 while the other cylinder is connected to the return line 88. Continued rotation of the cam will reverse the positions of the valves so that the first operating cylinder is connected to the return line and the second cylinder is connected to the supply line.

The valve spool 96 for the lirst valve 90 is urged against the cam 102 by a coil compression valve spring 104, which is held in the hollow valve body 94 by a split locking ring 106. The valve body 94 has ya port 108 which connects to the conduit 84 leading to the first operating cylinder 80 which slidably carries the operating piston 76. The valve port 108 is alterantely placed in communication with the Huid supply port 110, which is connected to the supply line 38, or the uid return port 112, which is connected tothe return line 88. Communication between the connecting port 108 and ports 110 and 112 is attained through the center relieved portion 114 of the dumbbell-shaped v-alve spool 96. When the valve spool is in the position shown in FIGURE l, port 108 communicates with port 110. When the cam 102 rotates to depress the valve spool 96, the port 108 is placed in communication with the return port 112, since the relieved portion 114 of the valve wil-l have moved to the left, the enlarged end 116 will have blocked the port 110, and the enlarged portion 118 at the left end of the valve spool will have moved away from port 112.

The inner construction of the valve 92 carrying the valve spool is identical with the valve 90 and, therefore, need not be described in detail. It is suliicient to state that the connecting port 120` of the Valve 92 is alternately connected to the return port 122, which connects to the return line 8S, or `to the supply port 124, which connects to the supply line 38.

Thus, rotation of the cam 102 on its supporting shaft 126 will alternate the valve spools 96 and 100 to alternate the supply of pressurized operating uid to the cylinders 80 and 82 to cause a reciprocation of the compressor piston. The speed of operation of the compressor piston 58 is thus determined by the speed of rotation of the alternator cam 102.

In some instances it may be desirable to use another form of compressor and control unit than that shown at 10 in FIGURE l. In these circumstances the compressor and control units shown in FIGURES 2 and 3 may be utilized.

For ease of identification of connecting lines with respect to FIGURES 1 and 2, the pressurized fluid supply lines in both rigores are marked S1 and S2 and the return lines for the operating fluid are marked R1 and R2. Also, the gas intake lines are marked I1 and I2 and the gas delivery lines are marked D1 and D2.

In the form of a compressor and control mechanism shown in FIGURE 2, -a compression piston 130 is slidably housed within a compression cylinder 132. The cylinder contains intake and delivery por-ts on each end which connect to the intake and delivery lines. The intake port forone side of the cylinder is shown at 132 and its correspending delivery port is shown at 134. The intake port 136 operates at the other side of the compression piston 130 and the delivery por-t 138 receives the compressed gas delivered by this side of the piston. The intake lines are each provided with a nonreturn check valve 140 and 142 which prevent escape of the gas when the piston is compressing gas on that side. The check valves also permit the intake of gas when the side of the piston exposed to the valve is moving in its` intake stroke. The discharge ports 134 and 13S are also provided with check valves 144 and 146, which prevent the return of gas from the delivery line. I

Connected to the compression piston 130 and in driving relation thereto, are oppositely disposed operating pistons 148 and 150. These pistons are slidably disposed in operating cylinders 152 and 154. The compression piston 130 may be provided with sealing means such as piston rings 156 and the operating pistons may also be provided withsirnilar piston or sealing rings 158 and 160.

Operating fluid is lalternately admitted to one of the cylinders and returned from the opposite cylinder by a control valve 162 for the cylinder 152, and 164 for the cylinder 154. The valves are illustrated as having a body 166 and 16S respectively, which is integral and projects from the end of the hollow cylinders 152 and 154. The valve bodies are centrally bored so that the spool valves 170 and 172 will be substantially coaxial with the operating pistons 148 and 150. The valve spools are movable between an operating fluid return position and an operating fluid supply position. The valve spool 172 is shown in the supply position wherein the cylinder 154 is connected to the supply line S2 to admit pressurized working iluid to the chamber 174 behind the operating piston 150 and move the operating and compressing piston assembly to the left in the direction shown by the arrow 176. For this movement the valve spool 170 at the opposite end is in the return position wherein its end 178 projects into the chamber 180 of the operating cylinder 152. As the piston assembly moves to the left in the direction of the arrow 176, the operating piston 148 engages the end 178 of the valve spool to push it to the supply position wherein the operating chamber 180 is connected to the supply line S1. The piston vassembly will then be forced to the right.

As soon as the left valve spool 170 is pushed to the supply position, pressurized operating fluid is admitted to the chamber 182 behind the right valve spool 172 to move it to the lluid return position.

The right and left valve spools 170 and 172 are identical in construction and, therefore, only one will be described in considerable detail. The left valve spool 170 has a central bore 184 which opens from the end 178 of the spool to communicate with the chamber 180 in the operating cylinder 152. Fluid flows into or out of the chamber through the valve `spool through a series of openings 186 annularly arranged yaround the central bore. These openings communicate with an annular groove 188 extending around the valve spool which in turn communicates with the annular groove 190 connecting to the lreturn line R1, or with the -annular groove 192 connecting to the supply line S1. The bore 184, the openings 186, Iand the groove 188 provide a first passage means for communication between the operating chamber 180 and the supply line or return line.

The valve spool 170 contains another annular ilow groove or second passage means 194 which functions to direct iiuid to the cross over line 196 connecting to the spool at the opposite end of the piston assembly. When the valve is in the iluid return position, as shown by the position of the valve spool 170, the annular groove 194 permits communication between the branch 197 connecting Ito the return line R1, and the cross over line 196. This vents the line 196 to the return line R1 and permits the valve spool 172 to move to its far right supply position. The valve spool 172 is held there by the pressure in the chamber 174.

The valve spool 170 also is provided with an enlarged end 198 having a working pressure responsive face 200 which forces the valve spool to the right or to the return position, when pressurized uid is present in the chamber 202 at the left end of the valve body 162. Pressurized fluid is in chamber 202 in the position shown in FIGURE 2 being directed there by cross over line 204, which is in communication with branch supply line 206 by means of the annular groove 208 in the right valve spool 172.

Summarizing `the operation of the piston assembly and control valve arrangement, the valve spool 172 is in the supply position with supply line S2 being in communication with the chamber 174 to which the operating piston 150 is exposed. The supply of uid Hows in through line S2, through the radial openings 210, through the axial bore 212 and into the operating chamber 174. The fluid pushes the piston 150 to the left and holds the valve spool 172 to the right. The chamber 182 behind the enlarged end 214 of valve spool 172 is vented `through cross over line 196, annular groove 194, and branch line 197 to return line R1. Pressurized fluid holds the left valve spool 170 in its return position by a pressurized fluid being present in the chamber 202 at the end of the valve spool 170 and being supplied there through cross over line 204, annular groove 208 in valve spool 172, and branch line 206, leading to supply line S2.

When the piston 150 has pushed the compressing piston 130 to the left end of its stroke, the left operating piston 14S will strike the valve spool 170 pushing it to the supply position.

As soon as the left valve spool 17 0 moves to the supply position, the branch line 218, connected to the supply line S1, passes fluid through the annular groove 194 in the valve spool 170, to the cross over line 196 to the chamber 182 behind the enlarged end 214 of the valve spool 172. This dn'ves the valve spool 172 to the fluid return position. Thus, fluid is admitted behind operating piston 148 and is relieved from behind operating piston 150. Spool remains in its supply position since line 204 is vented to the return line R2 by the annular groove 208 in the valve spool 172 bridging across to the branch line 220 connected to return line R2.

In using the form of the piston assembly and control valve arrangement of the FIGURE 3, the compressing piston and operating piston assembly is similar to FIG- URE 2. Compressing piston 222 is slidably housed in a compressing cylinder 224 which is provided with valved intake ports 226 and 228 and valved discharge ports 230 and 232. Each of these ports are connected to the intake lines and discharge lines as indicated by the letters I1, I2 and D1, D2.

At each side of the compression piston 222 is connected an operating piston as shown at 334 and 336. The operating pistons are slidably mounted in operating cylinders 338 and 340. Valve bodies 342 and 344 project coaxially beyond the operating cylinders `and carry valve spools 346 and 348.

The valve bodies or housings 342 and 344 are each provided with ports which connect to return lines R1 and R2 and to the supply lines S1 and S2 in the manner shown in FIGURE l .in the fluid supply arrangement. Each of the valve spools 346 and 348 is provided with an enlarged operating end 350 and 352. Each end has an outer working face exposed to a chamber 354 and 378, and these chambers are either subjected to the pressure of the operating fluid in the supply lines or to the fluid pressure in the return lines to move the valves to their return position or to their supply position. The valve spools 346 and 348 have a rst passage means 374 and 360' respectively, Which open into the operating chambers and cornmunicate with the supply lines S1 and S2, or the return lines R1 and R2 through radial portions 372 and 362 of the rst passage means. The spools also have second passage means 370 and 364 respectively for connecting the cross over lines to the supply or return lines.

ln the position of FIG. 3, the piston assembly, consisting of a compressing piston 222 and operating pistons 334 and 336, is moving to vthe right as shown by the arrow 356. The right valve spool 346 is in the lluid return position and the chamber 358, exposed to the end of the operating piston 336, is in communication with the return line R2 through the axial bored center passageway 360 through the valve spool and the radial passageway 362 leading to the annular relieved portion 364 of the valve spool.

The valve spool 346 at the opposite end of the assembly is in the supply position and the chamber 354 at the left end of the valve spool is subjected to the pressure or" the fluid return line R2 of the fluid through the cross over line 364, which connects to the annular relieved portion 364 of the right valve spool 348.

As the piston assembly moves to the right, the operating piston 336 will strike the end 366 of the valve spool 34? forcing it to the supply position.

The chamber 368 at the exposed end of the operating piston 334 is supplied with pressurized operating uid through the supply line S1, through the relieved portion 370 extending annularly around the valve spool 346, through the radial passageway 372, and through the axial drilled passageway 374 through the valve spool.

When the piston assembly moves to the extreme right of its path of travel, the operating piston 33'6 will strike the end 366 of the valve spool 348 moving it to the supply position. In this position the supply line S2 Will be in communication with the relieved portion 364 of valve spool 346 and a supply of iluid will ow through the radi-al passageway 362 and through the axial passageway 360 into the chamber 358 to move the piston assembly to the left. In this position, the cross over line 364, will also be in communication with the supply line S2, and the pressurized uid in the chamber 354 will force the Valve spool 346 to the return position where its end will project into the chamber 368. Up to the time the Valve spool 346 moves to the return position, the cross over line 376 has been connected to supply line S1 by the relieved portion 370 and the pressurized uid has been directed to chamber 378 Where it acted on the head 352 of the valve spool 348. When the valve spool 348 was pushed to the right by being struck by the piston 336, the head 352 of the valve was forced against the pressurized iuid in the chamber 378. Chamber 378 is connected to return line R1 when valve spool 346 is moved, however, and this will hold the valve spool 346 in its supply position.

Thus, the piston and valve control assemblies shown in FIGURES 1, 2 and 3 operate to cause a positive control of the operating uid and a quick positive reciprocation of the compressing piston. The valves are simple in operation and are identical in form, thereby enabling a long operating life and maximum efliciency without the aid of adjustment or attention,

The fluid control system meets the objectives hereinbefore set forth and enables the provision of an improved compressor which will operate to compress a gas such as is used in refrigerating systems and which will be operated by a uid at a higher pressure than the compressed gas.

The valve operation in FIGURES 2 and 3 is directly dependent upon the position of the operating pistons and with direct engagement of the valves a precisely timed operation is achieved. The compressed operating uid in the cylinder provides for a cushioning between the piston and the valve, but the valve is quickly and certainly operated without the necessity of providing an additional valve positioning or operating mechanism.

I have, in the drawings and specification, presented a detailed disclosure of the preferred embodiments of my invention, but it is to be understood that I do not intend to limit the invention to the specific forms disclosed, but intend to cover all modifications, changes and alternative constructions and methods falling Within the scope of the principles taught by my invention.

I claim as my invention:

1. A Huid operating motor comprising first and second connected opposed operating pistons, first and second opposed operating cylinders slidably housing the operating pistons, first and second sliding valve spools at the outer end of the first and second pistons individually movable between a supply position and a return position, means defining a first passage means through the individual valve spools communicating with the respective first and second operating cylinders and opening to the outer surface of the spools, means defining a second passage means in each of lthe valve spools, first and second valve cylinders slidably housing the valve spools having a closed end with the other end opening into the ends of the respective operating cylinders so that the operating pistons will engage the respective valve spools and move them from return position to supply position, said valve cylinders each having a supply port means connected to a source of pressurized fluid and opening through the 'valve cylinder wall and each having a return port means for venting fluid opening through the cylinder Wall, a first cross over line connected to the closed end of said second valve cylinder and opening through the wall of said first valve cylinder, and a second cross over line connected to the closed end of said first valve cylinder and opening into said second valve cylinder, said first passage means affording ldirect connection between said first and second operating cylinders and supply port means of the respective valve cylinders in the supply positions of the spools, and affording direct connection between said first and second operating cylinders and the respective return port means in the return position of the valve spools, said second passage means through said first and second valve spools respectively providing a direct connection through said valve spools between said first and second cross over lines and said supply port means in the supply positions of said respective first and second valve spools, and affording a direct connection through said valve spools between the return port means and said respective first and second cross over lines in the return position of the second valve spool.

2. A fluid operated motor in accordance with claim 1 in which each of said supply port means has a main port and a branch port and in which said return port includes a main port and a branch port and in which said first passage means communicates with said main ports and said second passage means communicates with said branch ports.

3. A fluid operating motor in accordance with claim 1 in which said first passage means and said second passage means are in communication within said valve spools.

References Cited in the file of this patent UNITED STATES PATENTS 547,768 Champ Oct. 15, 1895 1,595,458 Doolittle et al. Aug. 10, 1926 1,709,682 MoXley Apr. 16, 1929 '2,598,180 Kenyon May 27, 1952 2,797,666 Chubbuck July 2, 1957 2,829,501 Walls Apr. 8, 1958 FOREIGN PATENTS 12,990 Great Britain 1892 277,636 Great Britain Mar. 29, 1928 30,273 France Apr. 3, 1925 (2nd Addition to 567,394) 

